Intro to Neuro (J. Koning)

A collection of the most commonly seen findings,
cases, essential anatomy, and protocol pearls for
review in order to succeed on this rotation.
Jeff Koning, M.D.
Updated August 2012
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A good overview of Neuro CT protocols has
already been put together here:
http://radres.ucsd.edu/documents/Neuro/N
euro-CT-Tech.pdf
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As of the most recent revision of this document, CTAs of the
head and neck for stroke codes do not involve the
radiologist in protocolling the study. The CT techs should
call you when there is a stroke code.
Stroke code imaging includes:
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CTA of the head and neck, which includes a noncontrast CT of
the Head, CTA from the aortic arch to the skull vertex, and 3D
reformats of the CTA source images
CT soft tissue necks are almost always done with IV contrast
(one case where a CT of the neck without and with IV
contrast is needed is for calcified masses such as thyroid
CA). Sometimes ER orders CT soft tissue neck without IV
contrast and almost always they are wanting a cervical spine
CT, which should be protocolled by the bone resident
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CTs of the mandible are also misprotocolled
occasionally and end up on the bone list. Usually
when the ER orders CT mandible for facial trauma,
they are wanting a maxillofacial CT and these
should be protocolled without IV contrast.
Temporal bone studies are sometimes ordered as
“CT orbit/sella/ear” so be sure to look under the
indications and protocol it as a noncontrast
Temporal bone on the 64 slice scanner, if
appropriate
CT orbits are sometimes ordered for trauma when
a maxillofacial CT would be more appropriate to
further evaluate the potential for other facial
trauma
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The following slides cover the most essential
anatomy for success on the Neuro CT rotation
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Its called essential for a reason!
If you want more, all of the images above were
taken from StatDx, and there are plenty more
there!
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Noncontrast CT heads will be the most common
study you will need to interpret
You are usually given two head sequences with a
standard algorithm, one reconstructed with 2.5 mm slices
and another with 5 mm slices. The 5 mm slices are
preferred when looking at the brain parenchyma, as they
have less noise.
 You will also be given a head sequence with a bone
algorithm reconstructed with 2.5 mm slices. This is best
for looking at the sinuses, mastoid air cells, middle ear,
and of course, the bones.
 Finally, you will be given sagittal and coronal reformats
with a standard algorithm, which are best to look at
midline structures, cerebellar tonsil position, tentorium,
falx, subdural or epidural bleeds that may be difficult to
see on axial cuts, etc.
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Evaluating a noncontrast Head CT
As always, be systematic
 Windowing Hot Keys to know:
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2: Soft tissues
3: Bone
5: Best for CTA sequences
7: Brain Parenchyma
8: Gray/White differntiation or “Stroke” windows
9: Best for blood
Other windowing tips:
 It can be helpful to use bone windows to evaluate the petrous
ICAs and vertebral arteries around the skull base during CTA
evaluation
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Noncontrast maxillofacial CTs are commonly
ordered on trauma patients who have also had
head CTs
Save yourself time and only talk about the sinuses,
fractures, facial injuries, etc on one study and refer the
clinician to the other study for the intracranial findings
 Again, coronal and sagittal reconstructions will be given,
and orbital wall/maxillary wall fractures, midline
structures, etc will be better appreciated on theses
sequences
 Always ask for reconstructions if you notice they have
not been sent over by the techs
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The following slides include some common
findings and how to describe them that you
should be familiar with.
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Mucosal thickening
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Opacification
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A mucocele is essentially a mucous retention cyst that causes mass effect
(see next slide for example)
Bony thickening/sclerosis
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Also, describe it as partial, near complete, complete
Air fluid levels and bubbles indicate acute sinusitis
Mucous retention cyst/mucocele
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Grade it as either “Mild, Moderate, or Severe”
An indicator of chronic disease (see next slide)
Nasal polyps are not as commonly seen as the above findings
Typical dictations
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“Mild mucosal thickening is present within the right frontal sinus, right
maxillary sinus, and right ethmoid air cells. Query symptoms of acute
sinusitis.”
“Complete opacification of the right maxillary sinus with sclerotic changes
involving all walls of the right maxillary sinus, indicative of chronic
sinusitis.”
Below: mild mucosal thickening in the right maxillary
sinus, near complete opacification of the left maxillary sinus
with an air fluid level, near complete opacification and air
bubbles in the right sphenoid sinus, and moderate mucosal
thickening in the left sphenoid sinus. The mastoid air cells
are clear bilaterally. Impression: Pansinusitis
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Cerebrovascular calcifications
Grade as mild, moderate, severe
Commonly seen within the cavernous and supraclinoid internal
carotid arteries, as well as the distal V4 segments (intradural) of
the vertebral arteries
 Typical dictation: “Marked cerebrovascular calcifications are
present within the bilateral cavernous and supraclinoid internal
carotid arteries.”
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Other benign calcifications
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Bilateral globus pallidi (mention these in the findings only)
Pineal and choroid plexus (don’t mention these)
Remote neurocysticercosis (common) or granulomatous disease
Typical dications
 “Benign calcifications present within the bilateral globus pallidi.”
 “Scattered punctate calcifications present, consistent with remote
granulomatous disease versus neurocysticercosis.”
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Volume loss
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White matter hypoattenuation
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Choose one way to describe and stick with it
(Supratentorial/infratentorial, cerebral/cerebellar, diffuse, etc)
and qualify it with mild, moderate, severe or “greater than
expected for age”, or mild for age, or even “mild prominence of
the lateral ventricles and sulci, greater than expected for age.”
Usually seen in the periventricular or subcortical regions, and
while nonspecific, is most commonly due to hypertension or
chronic small vessel ischemia
Typical dictation: “Mild scattered nonspecific white matter
hypoattenuation is noted, likely secondary to HTN or chronic
microvascular ischemia.”
Old brain triad is cerebrovascular calcifications, white
matter hypoattenuation, and volume loss.
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Lacunar infarcts vs perivascular spaces
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There is a great discussion in Brant and Helms on
this
Typical dictations
 “Small hypodensity seen in the posterior limb of the
right internal capsule, likely sequelae of an old lacunar
infarct.”
 “Tiny hypodensity seen in the right putamen at the
level of the anterior commisure, likely a dilated
perivascular space versus old lacunar infarct.”
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The following slides are a few case examples
MR 26118042
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You will get this history frequently!
The following is a good example that they
aren’t always negative studies
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The following slide goes back over the
anatomy and indicates branches of the left
MCA that are occluded and those that aren’t
involved
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Many causes (thrombotic vs. embolic, dissection, vasculitis,
hypoperfusion)
Early: Critical disturbance in CBF
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Severely ischemic core has CBF < (6-8 cm³)/(100 g/min)
(normal ~ [60 cm³]/[100 g/min])
Oxygen depletion, energy failure, terminal depolarization, ion
homeostasis failure
Bulk of final infarct → cytotoxic edema, cell death
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 Later: Evolution from ischemia to infarction depends on many
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factors
 Ischemic "penumbra" CBF between (10-20 cm³)/(100 g/min)
 Theoretically salvageable tissue
 Target of thrombolysis, neuroprotective agents
Associated abnormalities
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Cardiac disease, prothrombotic states
Additional stroke risk factors: C-reactive protein, homocysteine
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DDx for Parenchymal Hypodensity
(Nonvascular Causes)
Infiltrating neoplasm (e.g., astrocytoma)
 Cerebral contusion
 Inflammation (cerebritis, encephalitis)
 Evolving encephalomalacia
 Dural venous thrombosis with parenchymal venous
congestion and edema
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The next slide gives the correlate MRI images,
but don’t worry about these because you’ll
only be reading CT during this rotation
They are obviously helpful to get a head start
for the future, however.
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CT perfusion is done occasionally in an effort
to locate the “penumbra”
There is a good discussion of this in Brant and
Helms
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This patient had other imaging done in the
neck which is shown on the following slides
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DIFFERENTIAL DIAGNOSIS
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Atherosclerotic Vascular Disease
 Smooth/irregular narrowing of proximal ICA, Ca++ in
arterial walls
 ICA, vertebrobasilar arteries most common sites
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Dissection
 Typically spares carotid bulb; no calcification
 Seen in young or middle-aged groups
 Smoother, longer narrowing without intracranial
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involvement
Fibromuscular Dysplasia
 "String of beads" > > long-segment stenosis
Vasospasm
 Usually iatrogenic (catheter-induced), transient
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Protocol
Color Doppler US as initial screen
 CTA/MRA or contrast MRA
 Consider DSA prior to carotid endarectomy, in equivocal
cases or if CTA/MRA shows "occlusion"
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Diagnostic Checklist
DSA remains "gold standard" but acceptable noninvasive
preoperative imaging includes any 2 of
 US, CTA, TOF, or contrast-enhanced MRA
 Late-phase DSA important to rule out "pseudo-occlusion"
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 High-grade stenosis with "string" sign
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Pathology
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NASCET method: % stenosis = (normal lumen minimal residual lumen)/normal lumen, x 100
Mild (< 50%), moderate (50-70%), severe (70-99%)
Treatment
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Carotid endarterectomy (CEA) if symptomatic
carotid stenosis ≥ 70% (NASCET)
Symptomatic moderate stenosis (50-69%) also
benefits from CEA (NASCET)
Asymptomatic patients benefit even with stenosis of
60% (ACAS)
ICA stenting depends on preoperative risk factors
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Extensively studied
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ACAS: Asymptomatic Carotid Artery Stenosis
NASCET: North American Symptomatic Carotid
Endarterectomy Trial
ICSS International Carotid Stenting Study in Europe
CREST: Carotid Revascularization Endarterectomy vs
Stenting Trial
SPACE: Stent-Supported Percutaneous Angioplasty of the
Carotid Artery versus Endarterectomy
EVA-3S: Endarterectomy versus Angioplasty in Patients
with Symptomatic Severe Carotid Stenosis
SAPPHIRE: Stenting and Angioplasty with Protection in
Patients at High Risk for Endarterectomy
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Large meta-analysis May 2012 in Ann Vasc Surg
Thirteen trials. 7,501 patients
Odds ratios (ORs) were calculated for CAS versus CEA.
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Risk of stroke or death within 30 days was higher after CAS than
CEA (OR = 1.57; 95% confidence interval [CI] = 1.11-2.22),
 especially in previously symptomatic patients (OR = 1.89; 95% CI =
1.48-2.41)
Stroke or death within 1 year was comparable (OR = 1.12; 95% CI =
0.55-2.30).
 Subgroup analysis, the risk of death and disabling stroke at 30
days did not differ significantly between CEA and CAS (death: OR
= 1.43; 95% CI = 0.85-2.40; disabling stroke: OR = 1.28; 95% CI =
0.89-1.83)
 Rate of nondisabling stroke within 30 days was much higher in the
CAS group (OR = 1.87; 95% CI = 1.40-2.50).
 The risks of myocardial infarction within 30 days and 1 year were
significantly less for CAS.
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Osborn, A. StatDx. Intracranial Internal Carotid
Artery. Accessed 7/25/12.
StatDX Neuroanatomy Images
Osborn, A. StatDx. Intracranial Arteries Overview.
Accessed 7/25/12.
Brownwyn, E. H. StatDx. Atherosclerosis,
Extracranial. Accessed 7/25/12.
Liu, Z. J. et al. Updated Systematic Review and
Meta-Analysis of Randomized Clinical Trials
Comparing Carotid Artery Stenting and Carotid
Endarterectomy in the Treatment of Carotid
Stenosis. Ann Vasc Surg. 2012 May; 26(4):576-90.